1. Field of the Invention
This invention relates to strontium titanate, hereinafter referred to as SrTiO.sub.3, films of the type produced by chemical vapor deposition (CVD) that are oriented so that the film's (100) face is parallel to the surface plane of the substrate. Such structures of this type, generally allow the SrTiO.sub.3 film to be deposited such that a high density capacitor or a buffer layer for a superconductor can be created.
2. Description of Related Art
There is a practical limitation of high transition temperature superconducting materials, hereinafter referred to as Hi-Tc materials, or the temperature at which the material becomes superconductive, especially, in the use of ceramics in a superconductor. Modified perovskites exhibit excellent superconductive properties but are brittle and cannot sustain any tensile strains. Such tensile strains develop, for example, when the superconductor is wrapped around a bobbin to form a superconductive winding for a magnet. It would then be desirable to mount the Hi-Tc material on a metal backing, forming a composite, which could withstand the tensile strains, then in applications such as superconductive windings, the conductor could be wound while keeping the Hi-Tc ceramic material on the neutral axis which should be practically strain free. Alternatively, the composite could be fabricated and wound in such a way as to put the Hi-Tc ceramic into slight compression.
Prior to the present invention, it was known in the production of substrates for superconductors to employ the use of a single crystal of a perovskite material such as SrTiO.sub.3. Such single crystals may even attain the size of up to 4" in diameter. See for example, U.S. Pat. No. 4,916,114 to Eckbardt Hoeing, entitled "Method for Producing a Layer-Like Composition of Oxide-Ceramic Superconducting Material". However, such single crystal substrates are impractical when being applied to superconductive windings because the single crystal can neither be grown long enough nor continuously wound on bobbins to fabricate magnets. Also, single crystals cannot be strung together conveniently to form an electrically continuous winding.
In another area concerning the production of buffer layers on a superconductive winding, a thin film of barium fluoride (BaF.sub.2) was used as a buffer layer between the metal substrate and the superconducting film. While the BaF.sub.2 buffer improved the superconducting properties of a YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor, hereinafter referred to as YBCO, the superconducting properties of the YBCO could be further improved if the buffer layer was constructed of a material, preferably, a perovskite, which is more compatible with the YBCO, which can be classified as a modified perovskite.
Finally, no attempts have been made to employ a CVD process for depositing material on a substrate which material can act as both a buffer layer for a superconductor and a high density capacitor. Further, the use of a CVD process to deposit material which is more compatible with the superconductor and can be deposited to form relatively pure buffer layers for the superconductor and high density capacitors would be still more advantageous.
It is apparent from above that there exists a need in the art for a material that can be deposited by a CVD process and also increases the superconductivity of the superconductive winding, and which can at least be deposited at the same deposition rates as known materials deposited by a CVD process, but which at the same time can create either a buffer layer for the superconductor or a high density capacitor. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.